This is weird.
I have iPhone 3g and iPhone 4 and dual-boot WinXP (SP3) and Win7 64 Ent. (SP1) - both iTunes updated
Now. In XP, everything is fine. Phones get recognised, iTunes syncs, they get charged. So... It's not cable, not computer or hardware related..
However, in Win7... iPhone 3g does not react. Not at all. I restart to XP... everything fine. Win7 - not.
Currently iPhone 3g gets charged with AC charger, but that's just weird ???
P.S. MSI motherboard with MSI super-charger started (or not - doesn't matter)

If that is the case, how come iPhone 4 is working correctly and I even upgraded it from 4.3.3 to 6.1.2 a few days ago... Thanks for trying to help, but I believe only someone that HAD the same problem can help because this is really the Twilight zone... I'll check the drivers, though..